LONDON, Jan 22 (Reuters) - The United Kingdom Independence Party, which transformed British politics by securing a referendum on EU membership, was plunged into chaos on Monday over the fate of its leader whose lover made racist comments about Prince Harry’s fiancee Meghan Markle.

Under Nigel Farage, UKIP became one of the most significant political forces in recent British politics by convincing former Prime Minister David Cameron to call a vote on EU membership and then campaigning successfully for Britain to leave.

But since Farage left after Brexiteers won the referendum, UKIP has descended into chaos, partly as its main aim - leaving the EU - is now the official policy of both the Conservative and Labour parties.

UKIP leader Henry Bolton has refused to resign since his 25-year-old lover, Jo Marney, made offensive comments about Markle and black people in text messages to a friend.

Marney who began dating Bolton just after Christmas, described U.S. actress Markle, whose father is white and mother is African-American, as a “dumb little commoner” and said “her seed with (sic) taint our royal family”, according to the texts printed in a Sunday newspaper.

Marney also described black people as ugly. She later apologised for the text messages and Bolton said they were ending their romantic relationship.

Bolton lost a vote of confidence from the party’s national executive committee but has insisted that he would not quit.

Led by the Farage, UKIP won nearly four million votes in 2015, 12.6 percent of those cast, on its anti-EU platform, projecting it to the forefront of British politics even though it only managed to win one seat in parliament.

Its popularity prompted Cameron, who once dismissed the party as being full of “fruitcakes, loonies and closet racists”, to hold the referendum and played a major role in securing a vote to leave the EU.

But since then it has been riven by internal strife and it won just 1.8 percent of the total votes cast in a national election last June.